The present invention relates to a draught beer dispensing system, and more particularly to a draught beer dispensing system which, can, in dispensing draught beer under pressure, automatically control pressure of carbon dioxide gas to be supplied into a draught beer receiving receptacle to an optimum pressure depending upon temperature of the draught beer to thereby automatically dispense a predetermined quantity of draught beer.
As a system for dispensing barreled draught beer, a draught beer dispensing system has been heretofore known. In such a draught beer dispensing system, pressurized carbon dioxide gases are supplied from a carbon dioxide cylinder into a keg filled with draught beer, and the draught beer within the keg is cooled in a cooling tank by the pressure of the thus supplied carbon dioxide gases and then dispensed.
There is a constant equilibrium relationship between temperature and pressure of draught beer filled in the keg. Taking, as an example, the case of 0.50% (5.0 g/) which is a standard content of carbon dioxide gas of the barreled draught beer, beer in 0.50% of carbon dioxide content assumes a stable state under the pressure of 2 kg/cm.sup.2 at 20.degree. C. This stable state herein termed means the just balanced state in which the carbon dioxide gas is no longer dissolved into beer nor liberated from the beer. Pressure at that time is generally called the equilibrium pressure. That is, in order that the carbon dioxide gases within the barreled draught beer may be always dispensed in a stable state, the equilibrium pressure according to the temperature of the beer has to be applied, which is a proper pressure. Accordingly, flat beer or foamy beer brings forth unless pressure of carbon dioxide gas supplied into a keg is set to an equilibrium pressure corresponding to temperature of draught beer when the draught beer is pressurized and dispensed from the keg, and therefore, pressure of the carbon dioxide gas supplied into the keg has to be controlled on the basis of the beer temperature. That is, when the pressure of carbon dioxide gases supplied into the keg is low, the carbon dioxide gases within the draught beer are liberated to bring forth flat beer with less content of carbon dioxide gas, whereas when the pressure of carbon dioxide gases supplied into the keg is high, the carbon dioxide gases are dissolved into the draught beer to bring forth foamy beer with much content of carbon dioxide gas. For this reason, a method for automatically controlling gas pressure within a draught beer receiving receptacle as disclosed in Japanese Laid-Open Patent Publication No. 64,790/1987 has been proposed. According to this controlling method, there comprises a pressure regulating member composed of a plurality of pressure reducing valves provided in parallel with each other to regulate pressure of carbon dioxide gases supplied from a carbon dioxide cylinder into a draught beer receiving receptacle, a temperature detection member composed of a temperature sensor for detecting a temperature of draught beer within the receiving receptacle, and a control member, whereby when the detection member detects that the temperature of draught beer within the draught beer receiving receptacle is higher than a predetermined temperature, the pressure of the supplied carbon dioxide gas caused by the pressure regulating member is increased by the control of the control member which receives a detection signal, whereas when the detection member detects that the temperature of draught beer within the draught beer receiving receptacle is lower than a predetermined temperature, the pressure of the supplied carbon dioxide gas caused by the pressure regulating member is decreased.
Next, one example of a conventional draught beer dispensing system will be described with reference to FIG. 29.
In FIG. 29, the reference numeral 1 designates a dispenser, which has a cooling coil 3 within a cooling tank 2, and a heat exchange is effected within the cooling coil 3 so as to cool beer within the cooling coil 3. On the end of the outlet side of the cooling coil 3 is provided a beer dispensing valve 110 called a tap which is opened and closed manually.
A draught beer keg 5 constituting a draught beer receiving receptacle is installed adjacent to the dispenser 1, and a dispenser head 6 is detachably mounted on the lip portion of the draught beer keg 5. The dispenser head 6 has a siphon pipe 7 suspended within the keg and a carbon dioxide gas supplying pipe 8 in communication with an upper part within the keg, the siphon pipe 7 being in communication with an inlet side of the cooling coil 3 by means of a beer hose 9, the carbon dioxide gas supplying pipe 8 being in communication with a carbon dioxide gas cylinder 13 through a manual pressure reducing valve 12 by means of a carbon dioxide gas hose 10.
In the aforementioned draught beer dispensing system, in the case where the draught beer within the draught beer keg 5 is dispensed, the carbon dioxide gases within the carbon dioxide gas cylinder 13 are supplied into the draught beer keg 5 through the pressure reducing valve 12, the draught beer within the keg 5 is supplied to the cooling coil 3 of the dispenser 1 through the siphon pipe 7 by pressure of the thus supplied carbon dioxide gases, and the beer dispensing valve 10 is opened to thereby dispense draught beer.
Next, a conventional beer dispensing valve will be described with reference to FIGS. 31 and 32.
A beer dispensing valve 110 shown in FIG. 31 is a manual dispensing valve having a foaming function. The beer dispensing valve 110 comprises a valve body 111, a valve stem 112 slidably provided within the valve body 111 and a lever 113 for sliding the valve stem 112, the valve stem 112 having a valve 114 provided at the front end thereof, the valve 114 being engaged with and disengaged from a valve seat 111a of the valve body 111 to perform a valve action.
The valve 114 is composed of a packing retaining member 115 slidably fitted in the front end of the valve stem 112 and a packing 116 held by the packing retaining member 115, and a compression coil spring 118 is interposed between the packing retaining member 115 and a nut 117 threadedly mounted on the front end of the valve stem 112. The nut 117 is formed at the front end thereof with a beer introducing small hole 117a, and the valve stem 112 is also formed with a foaming hole 112a.
With this arrangement, in dispensing draught beer as shown in FIG. 32(a), when the lever 113 is pulled down in a direction as indicated by arrow, the valve stem 112 slidably moves in a direction as indicated by arrow and the packing 116 of the valve 114 is disengaged from the valve seat 111a with the result that draught beer is dispensed from a nozzle 111n as indicated by arrow.
In FIG. 32(b), after a predetermined quantity of draught beer has been dispensed into a receptacle such as a mug, when the lever 113 is reversely pulled down, the valve stem 112 slidably moves in a direction as indicated by arrow, the packing 116 of the valve 114 becomes seated on the valve seat 111a to stop dispensing the draught beer, the packing retaining member 115 slidably moves against the biassing force of the compression coil spring 118 whereby the foaming hole 112a is opened with the result that the draught beer passes through the beer introducing small hole 117a and foaming hole 112a into a foam which is then dispensed from the nozzle 111n into a receptacle 45 such as a mug.
However, there is a constant equilibrium relationship between temperature and pressure of draught beer filled in the keg as previously mentioned. When this relationship is shown taking, as an example, the case of 0.50% which is a standard content of carbon dioxide gas of barreled draught beer, a temperature-pressure curve P.sub.L of beer shown in FIG. 30 is obtained. More specifically, when the draught beer temperature (.degree.C.) and pressure (kg/cm.sup.2) are taken on the axes of abscissa and ordinates, respectively, it is found that there is a regular (though non-linear) equilibrium relationship between temperature and pressure of draught beer. However, in the conventional control method disclosed in the aofrementioned Japanese Patent Laid-Open Publication No. 64790/1987, a plurality of pressure reducing valves provided in parallel with each other are selectively opened when draught beer is dispensed, and pressure of carbon dioxide gases supplied into the keg is stepwisely changed on the basis of the temperature of draught beer. This will be described in detail by way of an embodiment. When the draught beer temperature is less than 22.degree. C., pressure of carbon dioxide gases supplied into the keg is controlled to 1.75 kg/cm.sup.2 ; when the draught beer temperature is at 22.degree. C. to 29.degree. C., pressure of the carbon dioxide gases is controlled to 2.5 kg/cm.sup.2 ; and when the draught beer temperature is more than 29.degree. C., pressure of the carbon dioxide gases is controlled to 3.2 kg/cm.sup. 2. When this control is shown, a three-stage step-like pressure controll line C.sub.L is obtained as shown in FIG. 30.
Therefore, in the conventional control method, a rough pressure control partly far apart from the temperature-pressure curve P.sub.L of beer is carried out, which gives rise to a problem in that the pressure of the supplied carbon dioxide gases cannot be set to the equilibrium pressure corresponding to the temperature of draught beer to make it difficult to eliminate flat beer and foamy beer. On the other hand, in order to effect pressure control corresponding to the temperature-pressure curve P.sub.L of beer in the conventional control method, it is necessary to increase the number of pressure reducing valves to increase the number of steps in the pressure control line C.sub.L, to thereby allow the line C.sub.L to be coincident with the temperature-pressure curve P.sub.L of beer as much as possible. For this reason, the construction of system becomes complicated, and in addition, a number of valves have to be controlled, which therefore gives rise to a problem in that the control method becomes cumbersome.
On the other hand, in the conventional draught beer dispensing system shown in FIG. 29, the operation of the beer dispensing valve 110 is manually effected, and the opening and closing of the beer dispensing valve are manually effected. Therefore, this gives rise to a problem in that the constant amount of draught beer may not be uniformly dispensed into every receptacle such as a mug, such that some receptacles undergo excessive pouring or insufficient pouring. Therefore, predetermined quantity of beer cannot be always dispensed.
Furthermore, when draught beer is dispensed, both beer dispensing step and foaming step are carried out by manual operation of a lever of a beer dispensing valve. Therefore, an operator holds a receptacle 45 such as a mug or a paper cup by one hand and supports it at the nozzle 111n, and has to open and close a lever 113 of a tap by the other hand. Therefore, an operator cannot be moved away from a dispenser during dispensing draught beer into a receptacle, and since both hands are engaged, other works cannot be done simultaneously during that period of time.